Method and device for accessing maintenance functions of an aircraft from a mobile maintenance terminal

ABSTRACT

The invention in particular has as an object to access maintenance functions of an aircraft from a mobile maintenance terminal. First of all, the situation of the aircraft is determined ( 705 ). Then, if this situation allows a mobile maintenance terminal to access a maintenance information system on the ground and the information system of the aircraft, a connection is established ( 710 ) between the mobile maintenance terminal and the maintenance information system on the ground and at least one maintenance command intended for the information system of the aircraft is transmitted ( 730 ) to the said maintenance information system on the ground. If this situation allows the mobile maintenance terminal to access only the information system of the aircraft, a connection is established ( 740 ) between the mobile maintenance terminal and the information system of the aircraft and at least one maintenance command is transmitted ( 755 ) to the said information system of the aircraft.

This invention relates to maintenance operations of aircraft and moreparticularly to a method and a device for accessing maintenancefunctions of an aircraft from a mobile maintenance terminal. Access tothese functions varies according to the situation of the aircraft (inoperation or at its base).

In order to optimize the reliability of aircraft and to increase theirprofitability, maintenance operations frequently are implemented betweenflight phases. They may or may not be carried out when the aircraft isat its base.

In general, for maintenance operators such operations consist, forexample, in verifying the hardware and software configuration of thesystems of the aircraft, analyzing the data stored during the flight(ongoing monitoring), modifying certain parameters of the aircraft orcertain software data, launching test software applications and/orchecking the change of software configuration following a downloadingoperation.

The analyzed data often originate from sensors and are stored in acentral diagnostic and storage device accessible through a man-machineinterface of MCDU (abbreviation for Multi-Control Display Unit inEnglish terminology) or OMT (abbreviation for Onboard MaintenanceTerminal in English terminology) type. This interface, through whichinteractive operations may be launched, makes it possible to analyzestored data, access the parameters of the aircraft and more generally toexecute test and maintenance functions.

Access to the maintenance systems of aircraft generally is limited toon-board fixed physical stations in the cockpit. Thus, when the aircraftis on the ground, a maintenance operator may board the aircraft in orderto access and analyze the stored data, if need be modify the parametersof the aircraft, and launch test applications.

Alternatively, in order to meet a growing demand of the airlinecompanies to reduce the time of maintenance operations, mobilemaintenance terminals are used. The latter, the function of which issimilar to the interfaces of MCDU or OMT type, are connected to thecentral diagnostic and storage device through connection plugs connectedto the network of the aircraft.

FIG. 1 illustrates an exemplary aircraft 100 comprising a centraldiagnostic and storage device 105. This device is accessible, via aninternal communication network (not shown), at a maintenance terminal110, fixed or mobile. The mobile maintenance terminals generally arecalled PMAT (acronym for Portable Maintenance Access System in Englishterminology).

Device 105 is connected to all the systems of the aircraft generatingmaintenance messages, for example to sensors (not shown) for monitoringthe engines and the actuators for the landing gears and controlsurfaces.

In this way, when aircraft 100 is on the ground, with the aid ofterminal 110 a maintenance operator may analyze the flight data of theaircraft and modify the parameters thereof.

Furthermore, the airline companies operating these aircraft generallyhave maintenance information systems on the ground, also called MIS(acronym for Maintenance Information System in English terminology), inorder to ensure the tracking of the state of their fleet of aircraft.These information systems are operated in particular by maintenancecontrol centers, also called MCC (abbreviation for Maintenance ControlCenter in English terminology), and maintenance operators of the airlinecompany.

As illustrated on FIG. 1, data may be transmitted directly from anaircraft 100 to a maintenance information system of an airline company115, for example through an IP (abbreviation for Internet Protocol inEnglish terminology) type link. These data may be processed by themaintenance information systems for tracking the state of the fleet ofaircraft. Moreover, these data make it possible to build up theexperience acquired during the operation of the aircraft and thusoptimize maintenance operations.

In this way, although maintenance operations may be executed from amobile maintenance terminal and maintenance data originating from theaircraft may be used to optimize the maintenance operations, therenonetheless is a need to improve them.

The invention makes it possible to resolve at least one of the problemsset forth above.

The invention thus has as an object a method for a mobile maintenanceterminal to access maintenance functions of an information system of anaircraft, this method comprising the following steps,

-   -   determining the situation of the said aircraft;    -   if the said situation makes it possible to access a maintenance        information system on the ground and the said information system        of the said aircraft,    -   establishing a connection between the said mobile maintenance        terminal and the said maintenance information system on the        ground; and,    -   transmitting at least one maintenance command intended for the        said information system of the said aircraft to the said        maintenance information system on the ground;    -   if the said situation makes it possible to access only the said        information system of the said aircraft,    -   establishing a connection between the said mobile maintenance        terminal and the said information system of the said aircraft;        and,    -   transmitting at least one maintenance command to the said        information system of the said aircraft.

In this way the method according to the invention makes it possible toestablish a connection between a mobile maintenance terminal and aninformation system of an aircraft in order to ensure maintenancefunctions. This connection is, if possible, established via amaintenance information system on the ground in order to make itpossible to access a set of tools of this system, if need be. The methodaccording to the invention further enables a maintenance informationsystem on the ground to retrieve configuration data from an aircraft inorder to ensure management thereof.

If the said situation makes it possible to access a maintenanceinformation system on the ground and the said information system of thesaid aircraft, the method advantageously further comprises a step ofaccessing at least one information item from the said maintenanceinformation system on the ground to help an operator using the mobilemaintenance terminal to perform his maintenance task.

The method preferably further comprises a step of accessing at least onemaintenance datum from the said information system of the said aircraftin order to enable an operator using the mobile maintenance terminal toperform certain parts of his maintenance task.

According to a specific embodiment, the method further comprises a stepof securing the said mobile maintenance terminal if the said situationmakes it possible to access only the said information system of the saidaircraft so as not to create a weak point as regards the security of theinformation system of the aircraft.

Still according to a specific embodiment, the said connection betweenthe said mobile maintenance terminal and the said maintenanceinformation system on the ground or the said information system of thesaid aircraft is in compliance with the IP protocol. It preferably isestablished through a secured tunnel. Advantageously, a wirelessconnection is involved.

Still according to a specific embodiment, the method further comprises astep of receiving at least one execution result of the execution of thesaid at least one command in order to enable an operator using themobile maintenance terminal to perform certain parts of his maintenancetask.

The invention also has as an object a computer program comprisinginstructions adapted for the implementation of each of the steps of themethod described above when the said program is executed on a computeras well as a mobile maintenance terminal comprising means adapted forthe implementation of each of the steps of the method described above.

The advantages obtained with this computer program and this mobilemaintenance terminal are similar to those mentioned above.

Other advantages, purposes and characteristics of this invention becomeapparent from the detailed description that follows, presented by way ofnon-limitative example, with reference to the attached drawings inwhich:

FIG. 1 shows an aircraft comprising a central diagnostic and storagedevice able to be accessed by a maintenance terminal and able totransmit data to a maintenance information system on the ground;

FIG. 2 schematically illustrates the architecture of a part of theinformation system of an aircraft allowing an information system of anairline company to access data and maintenance functions of theaircraft;

FIG. 3 schematically illustrates an exemplary algorithm implemented inan information system of an aircraft to make it possible to accessmaintenance functions of the aircraft remotely;

FIG. 4 partially shows an Ethernet frame on which a filtering may beperformed;

FIG. 5 illustrates the first mode for connection of a PMAT to aninformation system of an aircraft, via a maintenance information systemon the ground;

FIG. 6 illustrates the second mode for connection of a PMAT to aninformation system of an aircraft;

FIG. 7 schematically illustrates an exemplary algorithm implemented in aPMAT to access data and maintenance functions of an aircraft; and

FIG. 8 illustrates an exemplary device adapted for implementing theinvention or a part of the invention.

In general, the invention makes it possible to perform maintenanceoperations in an aircraft from a mobile maintenance terminal (PMAT)according to two different modes linked to the situation of theaircraft, in operation or at its base.

It uses the information system, the maintenance functions and thecommunication means of the aircraft as well as the maintenance toolsdeployed on the ground and mobile maintenance stations in order toenable the maintenance operators to benefit from both modes of access tothe maintenance functions of the aircraft.

The communication means implemented among the information systems of theaircraft, the information systems on the ground and the mobile terminalspreferably are in compliance with the IP (abbreviation for InternetProtocol in English terminology) protocol.

According to a first mode implemented when the aircraft is at its base,the maintenance operator may access data and maintenance functions ofthe aircraft as well as information items from maintenance informationsystems on the ground (MIS). The operator thus has the means forestablishing a diagnosis of the aircraft, for consulting the databasesof the MIS and for performing the maintenance operations required toallow the aircraft to perform its missions and anticipate possiblefailures.

According to a second mode, the maintenance operator may access onlymaintenance data of the aircraft when the aircraft is not at its base.The operator thus has the means for establishing a diagnosis of theaircraft and for performing the maintenance operations necessary toallow the aircraft to continue its mission.

In the first mode, when the aircraft is at its base, the operator uses aPMAT configured to connect to the MIS, with a wired or wireless link.The MIS here comprises an interface making it possible to implement asecured connection with the aircraft giving it remote access to data andmaintenance functions. In this way the operator may connect to theaircraft via the MIS. He thus may access a considerable number ofinformation items enabling him to benefit from the real-time analysisand engineering skills of the ground crews.

In the second mode, when the aircraft is not at its base, themaintenance operator uses a PMAT configured to connect only to theaircraft on which the operator is going to intervene. In this mode, onlythe data and the maintenance functions of the aircraft are accessible.The maintenance operator therefore limits his intervention to thediagnosis of the aircraft and to the necessary maintenance operations,making it possible to ensure the level of safety required forcontinuation of the mission of the aircraft.

In this way the invention makes it possible to reduce the downtime ofaircraft on the ground and to improve the reliability of the maintenanceoperations by providing all the data useful to the maintenanceoperators.

It is seen here that, by default, when they are activated, the mobilemaintenance terminals try to connect to the MIS before attempting adirect connection to an aircraft in order to allow the maintenanceoperators to access the MIS information items, if possible.

The generation of the on-board information system in some modernaircraft depends on an architecture that allows the aircraft to beinterconnected with a data communication network on the ground viasecured IP communication means while ensuring that the components makingit possible to achieve aircraft safety are in accordance with therequired confidence level.

By way of illustration, the platform supporting the maintenancefunctions may be developed in accordance with the aeronautical standardDO-178B (standard for software development quality level according to agiven target, for example software quality assurance level DAL C).

The platform supporting the maintenance functions thus is such that theinformation items originating therefrom are reliable data.

Moreover, in order to ensure a sufficient level of data security, arobust data-flow filtering element is placed in particular in theinformation system of the aircraft. It allows the aircraft, via thesecured IP communication means, to be regarded as an extension of thenetwork of the airline company operating this aircraft withoutcompromising the safety thereof.

The information system of the airline company thus may retrieve datafrom the platform supporting the maintenance functions and execute thesefunctions in automatic and deported manner.

FIG. 2 schematically illustrates the architecture of a part of theinformation system of an aircraft allowing an information system of anairline company to access data and maintenance functions of theaircraft.

Reference 200 here designates the systems taken on board the aircraftwhile reference 205 designates remote systems of the airline companyoperating the aircraft.

The remote system comprises a remote station 210, for example a computerof PC (abbreviation for Personal Computer in English terminology) type,and a server 215 making it possible to establish a data communicationwith on-board information system 220 of the aircraft through network225.

Two types of data may be processed by the remote station or the teststation: the data originating from the aircraft and the command datamaking it possible to execute maintenance functions on board theaircraft.

On-board information system 220 of the aircraft is connected to avionicsystems 230, for example the flight control systems, the automatic pilotand the environmental monitoring systems, and to systems of thecommercial realm 235, referred to as “open,” unlike the avionic realm,because of the origin of the processed data.

Furthermore, on-board information system 220 comprises two parts, aspecially secured part 240, called confidence realm, and a less securedpart 245, called connected realm.

Less secured part 245 comprises communication module 250 adapted forreceiving and transmitting data from and to network 225, for exampleaccording to the IP protocol. Communication between server 215 andcommunication module 250 preferably is carried out through a securedtunnel such as a VPN (abbreviation for Virtual Private Network inEnglish terminology) link.

Communication module 250 is connected to a maintenance applicationmodule 255 that itself comprises an encoding module 260 used to encodethe data to be transmitted to secured part 240 of on-board informationsystem 220.

Secured part 240 comprises a filtering module 265 adapted forcontrolling the data transmitted by less secured part 245.

Secured part 240 further comprises a maintenance application module 270itself comprising a conversion module 275 adapted for converting thedata received from filtering module 265 so that they may be used bymaintenance application module 270.

As illustrated, maintenance application module 255 of less secured part245 is connected to the systems of the commercial realm 235 whilemaintenance application module 270 of secured part 240 is connected tothe systems of the avionic realm 230.

FIG. 3 schematically illustrates an exemplary algorithm implemented inan information system of an aircraft in order to allow remote access tomaintenance functions of the aircraft.

Reference {circle around (1)} here designates the part of the algorithmimplemented in the unsecured part of the information system of theaircraft, reference {circle around (2)} designates the part of thealgorithm implemented in the secured part of the information system ofthe aircraft, reference {circle around (3)} designates the functionsimplemented in the confidence realm, that is to say here the avionics,and reference {circle around (4)} designates the functions implementedin the commercial realm.

After having received a command (step 300) from a remote post via, forexample, a secured communication tunnel established beforehand, a testis performed (step 305) in order to identify the recipient of thereceived command.

If the recipient of the received command is located in the confidencerealm, the command is encoded (step 310) in order to make it compatiblewith the robust filter used at the input of the secured part, thentransmitted to the latter (step 315). The command and/or data exchangebetween the secured and unsecured parts preferably is carried out via adedicated internal network.

The encoding consists, for example, in encoding the commands in the formof frames having a predetermined format and/or characteristics. Thefiltering then consists in verifying this format and/or thesecharacteristics.

As indicated above, when the secured part of the information system ofthe aircraft receives a command from the unsecured part, the receivedcommand is filtered (step 320) with the aid of a robust filter. Thecommands not in accordance with the predetermined criteria of the filterare rejected. The filtered commands are converted or translated (step325) by a translation module of the secured part in order to allow theirexecution by the intended maintenance function.

The maintenance function sought, for example a test management module ora test configuration management module, executes the received command ormanages its execution and, preferably, sends a response, for example aconfiguration or a result, to the command translation module whichconstructs a corresponding file. This file then is transmitted (step330) to the maintenance function of the unsecured part of theinformation system of the aircraft which transfers the receivedinformation items to the remote station (step 335).

If the recipient of the received command is located in the connectedrealm, the command is encoded (step 340) in standard manner to make itcompatible with the protocols used in the systems of the connectedrealm. It then is executed (step 345) and, if a response is determined,the latter is transmitted to the remote station (step 335).

As indicated above, the filter has as an object to filter the datareceived from the network so as to transmit only the correctly formatteddata to the secured part of the information system of the aircraft.

The filtering module preferably is based on the principle of the screen,that is to say an iterative mechanism, according to which several levelsof filters are used to optimize the processing times. It thus iscomposed of several elements making it possible to filter the receiveddata more and more finely so as to let only the data corresponding tovalid commands go through. An example of such a robust filter isdescribed in the patent application FR 2 927 181 filed in the name ofthe company Airbus France.

The filtering module requires that a command format be defined so as toprocess only a certain type of network frames. The format and theassociated transport protocol may be defined in the form of parameters,accessible to the filtering module. For example, such parameters mayspecify that the commands are received in the form of Ethernet frames,indicate the sources authorized to transmit such commands, give amaximal lifetime for the frames beyond which the frames are not takeninto account and indicate the characters that may be used validly forencoding a command in a frame.

By way of illustration, the filtering of Ethernet frames may beperformed in three steps.

FIG. 4 partially shows an Ethernet frame 400 on which a filtering may beperformed according to these three steps.

First of all, each frame is analyzed by verifying, for example, sourcephysical address 405 and destination physical address 410, in particularthe MAC (acronym for Media Access Control in English terminology)addresses, type of protocol 415 and signature 425 of the complete frame.Data 420 of the frame are not analyzed in this first step.

If source physical address 405 and destination physical address 410,type of protocol 415 and signature 425 are not in accordance with theparameters of the filtering module, the frame is rejected.

On the contrary, if source physical address 405 and destination physicaladdress 410, type of protocol 415 and signature 425 are in accordancewith the parameters of the filtering module, a second filtering step isimplemented.

It should be noted here that the first filtering step may focus on dataother than those mentioned or, on the contrary, fewer data.

The second step consists, for example, in analyzing the header of thedata 420. In particular, this second filtering step may consist inverifying IP version 425, length 430 of the header, type of service 435,total length 440 of the data, identification 445 used to reconstitutethe fragments, lifetime 450, also called TTL (abbreviation for Time ToLive in English terminology), protocol 455 and source address 460 anddestination address 465.

Again, if all these information items are not in accordance with theparameters of the filtering module, the frame is rejected. On thecontrary, if all these information items are in accordance with theparameters of the filtering module, a third filtering step isimplemented.

It also should be noted here that the second filtering step may focus ondata other than those mentioned or, on the contrary, fewer data.

The third step here consists in analyzing the characters of the usefuldata 470 of the frame. This step thus makes it possible to verify thatthe characters necessary for construction of the command may not be usedto construct an executable code. Advantageously, all the characters ofthe useful data should be chosen in the ASCII table, in the valuesranging between 032 and 090.

If a character of the useful data 470 does not belong to the ASCIItable, between the values 032 and 090, the frame is rejected. On thecontrary, if all the characters of the useful data 470 belong to theASCII table, between the values 032 and 090, the frame is transmitted tothe secured part of the information system of the aircraft to beprocessed there.

Naturally, the third filtering step may focus on other criteria, inparticular more restrictive criteria.

The translation of filtered commands has as an object to establish aninterface between the maintenance functions and the network.

This module preferably is developed so that only the commands linked toinstructions corresponding to maintenance functions implemented in thesecured part of the information system of the aircraft have an effect.This means that this module knows the instructions that may be executedby each application. In other words, a list of instructions or sequenceof instructions preferably is stored beforehand. Such a list defines aset of configurations of possible strings of instructions. This listalso may define prohibited combinations.

This configuration is constructed in such a way that the string ofinstructions for an application is known a priori. This enables theconversion to verify that the commands that it receives and the stringof the associated instructions are in accordance with what theapplication is supposed to execute. This verification enables theconversion module to reject any unexpected string and thus ensures thatdangerous operations cannot be executed.

In a specific embodiment, the conversion module uses a table ofcorrespondence between the names of the commands and the actualfunctions, that is to say the sequences of instructions, so as toassociate one or more instructions with the names of commands receivedfrom the remote station. It should be noted here that the instructionsmay take several forms. For example, pointers to functions or commandsinterfaced with the operating system of the maintenance device areinvolved. The instructions make it possible in particular to simulate anaction input by a user on the interface of the maintenance deviceaccessible in the aircraft.

After a command has been analyzed and declared in conformity, theconversion module transmits the instructions corresponding to theapplication concerned. The application executes the instructions andgenerally sends back a response. This response is received by theconversion module which constructs a response message, preferablysigned.

FIG. 5 illustrates the first mode for connection of a PMAT to aninformation system of an aircraft, via a maintenance information systemon the ground, for example a ground maintenance system of an airlinecompany operating this aircraft.

As indicated above, when a PMAT is activated, it first attempts toconnect to an information system on the ground before trying to connectto that of an aircraft. These connections, wired or wireless, aresecured.

Thus when PMAT 500 is connected to communication network 225 to which anMIS 505 also is connected, it connects to the latter according to astandard protocol. More precisely, PMAT 500 connects to a server 215 ofMIS 505 to which tools and databases (not shown) of the airline companyoperating the aircraft may be connected.

Similarly, information system 220 of an aircraft may connect to MIS 505via network 225 or a separate network. For these purposes, server 215here connects to part domain 245 of information system 220 viacommunication module 250 (not shown). As indicated above, part 245 isconnected to the systems of commercial realm 235 as well as tomaintenance applications 270, via robust filter 265, to which theavionics 230 is connected.

Advantageously, PMAT 500 and information system 220 are connected tocommunication network 225 by a wireless link. Moreover, in order toensure the mobility of the maintenance operator around and in theaircraft, a wireless network of the aircraft is configured as anextension of network 225 so as to allow connection of PMAT 500 to MIS505 via this wireless network of the aircraft. This particular functionthat may be implemented in certain wireless aircraft networks thusensures an itinerancy function (called roaming in English terminology)for the PMAT between the outside and the inside of the aircraft.

When these connections are established, PMAT 500 may access informationitems from MIS 505 as well as data and maintenance functions of theaircraft via MIS 505.

FIG. 6 illustrates the second mode for connection of a PMAT to aninformation system of an aircraft.

This communication mode is implemented when the PMAT is unable toconnect to a maintenance information system on the ground. In this case,after having been activated and having attempted to connect to amaintenance information system on the ground, it endeavors to connectdirectly to that of an aircraft. This connection, wired or wireless, issecured.

For these purposes, PMAT 500 connects to part 245 of information system220 via communication module 250 (not shown). As indicated above, part245 is connected to systems 235 of commercial realm 235 as well as tomaintenance applications 270, via robust filter 265, to which theavionics 230 is connected.

When this connection is established, PMAT 500 is able to access data andmaintenance functions of the aircraft.

FIG. 7 schematically illustrates an exemplary algorithm implemented in aPMAT for accessing data and maintenance functions of an aircraft.

After having been activated (step 700), the PMAT performs a first testto determine the accessible maintenance information systems (step 705).This step may consist in identifying the communication networks able tobe used by the PMAT and/or the maintenance information systemsaccessible via the communication networks and able to be used.

If a maintenance information system on the ground is accessible, thePMAT connects thereto (step 710).

The PMAT then may access certain information items from the MIS (step715).

At the same time or sequentially, a test is performed (step 720) todetermine whether the aircraft on which the maintenance operator usingthe PMAT is to perform maintenance operations is accessible, that is tosay whether it is connected to the MIS.

This verification may consist in particular in verifying that anidentifier of the aircraft considered is present in the list ofidentifiers of aircraft connected to the MIS.

If not, a failure message is transmitted to the maintenance operator.

If the aircraft is connected to the MIS and if the PMAT has rightsallowing it to perform a maintenance operation, the maintenance operatormay use the PMAT to access the “open” maintenance data (step 725), thatis to say the maintenance data available in part 245 of informationsystem 220 of the aircraft.

In this case, the maintenance operator also may use his PMAT to send outmaintenance commands (step 730), for example a test request to anavionic equipment item or a request intended to obtain maintenance datafrom the confidence realm. These commands are transmitted to the MISwhich translates them according to a predetermined format compatiblewith the information system of the aircraft and transmits them thereto.

After reception of these translated commands, the information system ofthe aircraft analyses them and, if need be, creates the command or theset of commands requested. The commands created are compatible with therobust filter used to protect the avionics. They are transmitted to themaintenance applications accommodated in the confidence realm whichexecute them and preferably construct a result file which is transmittedto the communication module of the information system of the aircraft tobe retransmitted to the MIS which advantageously creates a page that maybe displayed from the PMAT (step 735).

Thus, in this operating mode, the maintenance operator may access dataand maintenance functions of the aircraft as well as information itemsfrom the MIS. That allows him to benefit from the expertise of theentire maintenance community of the airline company operating theaircraft in order to perform the required maintenance operations.

If no maintenance information on the ground is accessible and aninformation system of an aircraft is accessible, the PMAT connectsthereto (step 740).

In this case, the PMAT is first of all configured to be compatible withthe safety level of the aircraft. This configuration has as an object tolimit the capabilities of the PMAT, particularly in terms ofcommunication and execution of applications (only communications andapplications expressly accepted may be implemented in thisconfiguration).

If the PMAT has rights allowing it to perform a maintenance operation,the maintenance operator may use the PMAT to access the “open”maintenance data (step 745), that is to say all the maintenance dataavailable in part 245 of information system 220 of the aircraft. Themaintenance operator thus may access, in particular, the electroniclogbook, called e-logbook in English terminology, and consult the listof failures for which a repair is necessary.

Depending on the failure messages, the maintenance operator must be ableto access the maintenance functions of the confidence realm. For thesepurposes, the maintenance operator may use his PMAT to send outmaintenance commands to execute maintenance functions on board theaircraft and/or to access maintenance data of the confidence realm.These commands are transmitted in a predetermined format compatible withthe information system of the aircraft. They therefore are encoded thentransmitted (steps 750 and 755).

After reception of these commands, the information system of theaircraft analyses them and, if need be, creates the command or the setof commands requested. The commands created are compatible with therobust filter used to protect the avionics. They are transmitted to themaintenance applications accommodated in the confidence realm whichexecute them. These commands concern, for example, an electrical switchcommand, a test command or a software loading command.

A result of execution of the command preferably is drawn up by themaintenance functions to be transmitted to the communication module ofthe information system of the aircraft which retransmits it to the PMAT(step 760).

According to a specific embodiment, the result of the maintenanceoperation is analyzed by the maintenance function of the connected realmin order, preferably after confirmation, to update the electroniclogbook and enable it to process a subsequent failure, if need be.

Thus, in this operating mode, the maintenance operator may access dataand maintenance functions of the aircraft.

As illustrated by the dotted-line arrows, the steps of transmitting acommand as well as accessing data and information items may be repeated.

In this way the two operating modes of the PMAT enable a maintenanceoperator to use a single portable maintenance terminal, irrespective ofthe situation of the aircraft, at its base or not, while allowing him tobenefit, if possible, from the expertise of the entire maintenancecommunity of the airline company operating the aircraft.

A device adapted for implementing the invention or a part of theinvention is illustrated on FIG. 8. Device 800 is, for example, aportable computer of PC type.

Device 800 here comprises a communication bus 802 to which there areconnected:

-   -   a central processing unit or microprocessor 803 (CPU, Central        Processing Unit);    -   a read-only memory 804 (ROM, acronym for Read Only Memory in        English terminology) that may comprise programs “Prog,” “Prog1”        and “Prog2”;    -   a random-access memory or cache memory 806 (RAM, acronym for        Random Access Memory in English terminology) comprising        registers adapted for recording variables and parameters created        and modified during execution of the aforementioned programs;        and,    -   a communication interface 818 adapted for transmitting and        receiving data.

Preferably, device 800 furthermore has:

-   -   a screen 808 for displaying data and/or serving as a graphical        interface with the user who will be able to interact with the        programs according to the invention, with the aid of a keyboard        and a mouse 810 or another pointing device such as a light pen,        a touch screen or a remote control;    -   a hard disk 812 that may comprise the aforementioned programs        “Prog,” “Prog1” and “Prog2” and data processed or to be        processed according to the invention; and,    -   a memory card reader 814 adapted for receiving a memory card 816        and for reading or writing therein data processed or to be        processed according to the invention.

The communication bus allows communication and interoperability amongthe different components included in device 800 or connected thereto.The depiction of the bus is not imitative and, in particular, thecentral unit is capable of communicating instructions to any componentof device 800 directly or through another component of device 800.

The executable code of each program allowing the programmable device toimplement the processes according to the invention may be stored, forexample, in hard disk 812 or in read-only memory 804.

According to a variant, memory card 816 may contain data, in particularsignature keys, as well as the executable code of the aforementionedprograms which, once read by device 800, will be stored in hard disk812.

According to another variant, the executable code of the programs willbe able to be received, at least in part, through interface 818, to bestored in a manner identical to that described above.

More generally, it will be possible for the program or programs to beloaded into one of the storage means of device 800 before beingexecuted.

Central unit 803 is going to control and direct the execution of theinstructions or portions of software code of the program or programsaccording to the invention, which instructions are stored in hard disk812 or in read-only memory 804 or else in the other aforementionedstorage components. During boot-up, the program or programs that arestored in a non-volatile memory, for example hard disk 812 or read-onlymemory 804, are transferred into random-access memory 806 which thencontains the executable code of the program or programs according to theinvention, as well as the registers for storing in memory the variablesand parameters necessary for implementation of the invention.

Naturally, in order to meet specific needs, an individual competent inthe field of the invention will be able to apply modifications in theforegoing description.

1. Method for a mobile maintenance terminal to access maintenancefunctions of an information system of an aircraft, this method beingcharacterized in that it comprises the following steps, determining(705) the situation of the said aircraft; if the said situation makes itpossible to access a maintenance information system on the ground andthe said information system of the said aircraft, establishing (710) aconnection between the said mobile maintenance terminal and the saidmaintenance information system on the ground; and, transmitting (730) atleast one maintenance command intended for the said information systemof the said aircraft to the said maintenance information system on theground; if the said situation makes it possible to access only the saidinformation system of the said aircraft, establishing (740) a connectionbetween the said mobile maintenance terminal and the said informationsystem of the said aircraft; and, transmitting (755) at least onemaintenance command to the said information system of the said aircraft.2. Method according to the preceding claim further comprising, if thesaid situation makes it possible to access a maintenance informationsystem on the ground and the said information system of the saidaircraft, a step of accessing (715) at least one information item fromthe said maintenance information system on the ground.
 3. Methodaccording to claim 1 or claim 2 further comprising a step of accessing(725, 745) at least one maintenance datum from the said informationsystem of the said aircraft.
 4. Method according to any one of thepreceding claims further comprising a step of securing the said mobilemaintenance terminal if the said situation makes it possible to accessonly the said information system of the said aircraft.
 5. Methodaccording to any one of the preceding claims according to which the saidconnection between the said mobile maintenance terminal and the saidmaintenance information system on the ground or the said informationsystem of the said aircraft is in compliance with the IP protocol. 6.Method according to the preceding claim according to which the saidconnection between the said mobile maintenance terminal and the saidmaintenance information system on the ground or the said informationsystem of the said aircraft is established through a secured tunnel. 7.Method according to any one of the preceding claims according to whichthe said connection between the said mobile maintenance terminal and thesaid maintenance information system on the ground or the saidinformation system of the said aircraft is a wireless connection. 8.Method according to any one of the preceding claims further comprising astep of receiving (735, 760) at least one execution result of theexecution of the said at least one command.
 9. Computer programcomprising instructions adapted for the implementation of each of thesteps of the method according to any one of the preceding claims whenthe said program is executed on a computer.
 10. Mobile maintenanceterminal comprising means adapted for the implementation of each of thesteps of the method according to any one of claims 1 to 8.